The present invention relates to a remote control system for remotely controlling various electronic devices, and more particularly to a remote control system for remotely controlling devices such as AV (audio visual) devices by way of voice commands.
In recent years, various AV devices such as stereo sets, television receivers, cassette tape decks, video tape decks, compact disc players, laser vision disc players, or the like are equipped with remote control systems.
A remote control system has a transmitter which is usually positioned remotely from a controlled AV device. The transmitter, when operated, transmits a remote control signal, such as an infrared remote control signal, which is received by a receiver in the controlled AV device. The received remote control signal is decoded to control the AV device as intended by the remote control signal.
There has recently been developed a voice-operated remote control system which employs voice control commands instead of control commands entered through keys. The voice-operated remote control system has a microphone mounted on a transmitter for converting a voice command into an electric voice signal, and a speech recognition LSI (Large Scale Integration) circuit for generating a remote control signal which corresponds to a voice pattern represented by the voice signal. The remote control signal thus generated is transmitted to a receiver in a controlled AV device.
The first problem with the voice-operated remote control system is that the microphone for receiving voice commands tend to pick up noise other than the voice commands, and the accuracy of speech recognition (speech recognition rate) is lowered by such noise.
According to one process of speech recognition, voice patterns of voice commands of the operator are registered as standard patterns, and a voice command which is entered by the operator during normal use is compared with the standard patterns to determine similarity therebetween. The standard pattern which has high similarity is then regarded as the input voice command. One drawback of such a speech recognition process is that if there is ambient noise near the microphone of the remote control system at the time of registering voice commands of the operator, then standard patterns are registered as combinations of the voice commands and the ambient noise, and a voice command which is actually entered may be recognized in error if there is no ambient noise. Another drawback is that even if the operator's voice commands are registered correctly, an actual voice command may not coincide with the registered standard pattern if there is ambient noise during use, and the voice command may be recognized in error.
The second problem with the voice-operated remote control system is that sounds reproduced by the speakers of a stereo set, for example, may act as ambient noise.
More specifically, the transmitter of a conventional voice-operated remote control system transmits remote control signals regardless of how an information reproducing device, which is remotely controlled by the remote control system, operates. As a result, if the information reproducing device is a device which acoustically reproduces recorded signals through speakers, e.g., a stereo set, then reproduced sounds other than voice commands exist around the microphone of the transmitter.
If the intensity of reproduced sounds from the information reproducing device is relatively high, such reproduced sounds as well as voice commands are picked up by the microphone. This results in a reduction in the speech recognition rate of the speech recognition unit in the voice-operated remote control system.
The third problem of the voice-operated remote control system is connected with adjustment of the speech recognition rate. According to one speech recognition process in the conventional voice-operated remote control system, a voice command which is entered through the microphone is converted into pattern data, which are then compared with a plurality of standard pattern data that have already been stored, so that the distance between the voice command pattern data and the standard pattern data is determined. If one of the standard pattern data has the smaller distance to the voice command pattern data and satisfies predetermined recognition conditions (e.g., the distance is smaller than a given distance), then command data which correspond to the standard pattern data are outputted. If all the standard pattern data fail to satisfy the predetermined recognition conditions, then a rejection signal representative of a recognition failure is outputted.
In cases where no proper speech recognition is achieved and rejection signals are produced frequently, then the operator may manually modify the predetermined recognition conditions or register standard pattern data again for thereby increasing the speech recognition rate. However, the manual modification of the recognition conditions is inconvenient and tedious for the operator.
The fourth problem of the voice-operated remote control system is addressed to disagreement between voice command words and registered standard patterns. Standard patterns which are necessary for speech recognition are produced by registering operator's voice commands as pattern data in advance. When the voice commands are to be registered, it is customary to simplify the voice commands or use key words for the voice commands. For example, a control command indicating that the playback process of a CD player should be started is converted into a voice command uttering "PLAY". Since such standard pattern data are registered extracting only features of voice commands, it is not possible to reconstruct original voice commands from the standard pattern data. Therefore, if the operator happens to forget a voice command registered as standard pattern data, then the operator is unable to control the controlled device using voice commands. When this happens, the operator has to register voice commands again, but such a process is tedious and time-consuming.